X25519(7ossl)

✨ NAME ✨

X25519, X448 — the whole EVP_PKEY support situation for X25519 and X448, bestie 💅

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🦋 DESCRIPTION 🦋

Okay so the X25519 and X448 EVP_PKEY implementation lowkey supports key generation and key derivation using X25519 and X448. It comes with associated private and public key formats that are compatible with RFC 8410 ✨

And just so we're clear: no additional parameters can be set during key generation. Like, none. That's the vibe.

When you're performing key derivation, the peer public key must be set using EVP_PKEY_derive_set_peer() 🫶

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💅 NOTES 💅

You can get a context for the X25519 algorithm by calling:

EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X25519, NULL);

For the X448 algorithm, get a context by calling:

EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X448, NULL);

X25519 or X448 private keys can be set directly using EVP_PKEY_new_raw_private_key(3), or loaded from a PKCS#8 private key file using PEM_read_bio_PrivateKey(3) (or a similar function). Completely new keys can also be generated — see the example below, bestie 👀 Setting a private key also sets the associated public key. Iconic behavior, honestly.

X25519 or X448 public keys can be set directly using EVP_PKEY_new_raw_public_key(3), or loaded from a SubjectPublicKeyInfo structure in a PEM file using PEM_read_bio_PUBKEY(3) (or a similar function) 🌸

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🎀 EXAMPLES 🎀

This example generates an X25519 private key and writes it to standard output in PEM format:

#include <openssl/evp.h>
#include <openssl/pem.h>
...
EVP_PKEY *pkey = NULL;
EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X25519, NULL);
EVP_PKEY_keygen_init(pctx);
EVP_PKEY_keygen(pctx, &pkey);
EVP_PKEY_CTX_free(pctx);
PEM_write_PrivateKey(stdout, pkey, NULL, NULL, 0, NULL, NULL);

The key derivation example in EVP_PKEY_derive(3) can be used with X25519 and X448 🦋

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🌈 SEE ALSO 🌈

• EVP_PKEY_CTX_new(3)
• EVP_PKEY_keygen(3)
• EVP_PKEY_derive(3)
• EVP_PKEY_derive_set_peer(3)

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👑 COPYRIGHT 👑

Copyright 2017-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

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That's the tea, bestie — source/version 3.5.9, dated 2026-09-29. Stay iconic, and may your keys be ever in your favor 💖✨